Improved autoinjector supporting the syringe at the front

ABSTRACT

An autoinjector comprising a housing in which can be mounted a syringe comprising a barrel for holding a volume of medicament, a needle at one end of the barrel in fluid communication with the medicament and a plunger axially-moveable in the barrel to a forwardmost position, the autoinjector further comprising a syringe support means for supporting the barrel at an axial location at or forward of the forwardmost position of the plunger and having a reaction surface for the syringe, whereby in use said reaction surface ( 109 ) provides an axial compressive force on said barrel when a forward axial force is applied to the plunger.

This invention relates to the field of autoinjectors for theadministration of liquid medication, for example, interferon.

BACKGROUND

An autoinjector is an automatic injection device designed to facilitateautomated delivery of a dose of medicament to a patient through ahypodermic needle, the injection usually being administered by thepatient themselves. An autoinjector works, for example, by delivering aninjection automatically upon actuation by the patient pressing a button,moving a lever or part of a housing etc. This is in contrast to aconventional manual syringe where the patient himself needs to directlydepress a plunger into a barrel containing medicament in order to effectthe injection. The terms “autoinjector” and “injection device” are usedinterchangeably in the following description.

Examples of autoinjectors are described in WO2003/099358 (Seedlings LifeScience Ventures LLC) and WO01/93926 (Mayo Foundation for MedicalEducation and Research). These are both generally flat devices which areof small size to encourage users to carry the device with them for readyaccess. GB2396298 (PA Consulting Services Ltd) is an example of a moreconventionally-shaped elongate autoinjector, but of relatively complexinternal construction.

All three of the above prior art devices have a custom designedmedicament chamber therein rather than being built around a standardpre-filled syringe presentation. The custom medicament chamber, althoughallowing for a compact overall size for the device, means that thedevice as whole must be subjected to more rigorous regulatory control ascompared with a device containing a standard pre-filled syringepresentation which will have already obtained regulatory approval.

Another reason why the above prior art cannot be used in conjunctionwith a standard syringe presentation is related to the needle. Usually,a standard pre-filled syringe presentation to be used within adisposable autoinjector includes a needle in communication with amedicament chamber contained within the barrel of the syringe. It isessential that the sterility and integrity of the needle is maintainedand protected right up until the moment it is required to deliver aninjection. Usually this is achieved by providing a needle sheathcomprising a solid (for example an elastomer such as rubber) sheath intowhich the needle is staked or spiked so that it is surrounded and sealedon all sides. Usually, at least the forwardmost 3-4 mm of the needle isembedded in the rubber of the needle sheath. The autoinjector cannot beoperated with the needle sheath in place. Immediately prior to actuatingthe device, the user removes the needle sheath, for example by removingan endcap from the device to which the needle sheath is attached, sothat the needle is ready for use. In contrast, WO01/93926 for examplehas an entirely different type of needle sheath 79 which is designed tobe ruptured by the forward-moving needle during use of the autoinjector.In other words, this type of rupturable needle sheath does not need tobe removed from the device before actuation, however, such needlesheaths are likely to provide less mechanical protection than thoseprovided in a standard pre-filled syringe presentation and usually donot directly maintain sterility of the medicament and the needle.

In general, an autoinjector includes a needle which is located withinthe housing of the device. Upon activation of a force-generating source,a portion of the needle extends out of the housing and penetrates theouter layer of skin to deliver medicament. In some known autoinjectors,after activation, a needle cover or needle shield moves forward toconceal the needle after use. In GB2396298, the needle automaticallyretracts back into the housing by means of a biasing spring.

An improved autoinjector is described in our co-pending internationalpatent application, published under number WO 2005/070481. Some of thereference numerals in the present application correspond with theequivalent components in the device described in WO 2005/070481. Thisdevice requires that the needle is moved axially so that it can appearbeyond the end of the nozzle for the duration of the injection, afterwhich the needle retracts automatically, so that it is never in sight ofthe user. The device also requires that the plunger is moved axially sothat medicament is ejected. The overall complexity of the autoinjectoris significantly reduced by both of these requirements being effected byone component, namely an inner housing and the device has thesignificant advantage that it can be built around a conventional orstandard syringe presentation.

The injection device of WO 2005/070481 is designed to be used inconjunction with a standard drug presentation e.g. a pre-filled syringecomprising a needle, barrel pre-filled with medicament and a plunger.The plunger may include a separately-provided plunger rod. As mentionedabove, there is a significant commercial advantage in being able to usea standard pre-filled syringe, which will have been subjected tonumerous clinical trials, drug stability studies and regulatoryapproval. Any modification to the standard syringe may require furthertrials and approval, adding delay and expense. The present invention isrelevant to any injection device for use in conjunction with a standardpre-filled syringe presentation (whether preloaded or not and whethersingle-use or reusable), not only the device described in WO2005/070481.

The barrel of a syringe is usually glass, since glass has the mostfavourable storage properties for many drugs. However, glass isnotoriously fragile and there is a risk of damage or breakage of thesyringe during injection if the forces to which the syringe is subjectedby the injection device are not properly controlled. This isparticularly so where the liquid medicament is relatively viscous,requiring greater force to expel it from the syringe via the needle.Barrels made of materials other than glass, for example polyethylene orcyclic olefin polymers are less brittle when subjected to normal forcesduring injection, but still would benefit from the invention describedbelow.

In the known device described in our co-pending patent application no WO2005/070481 and illustrated in FIGS. 1-3 of the present application, thesyringe is supported within the injection device by a barrel or syringeholder 9. The syringe holder 9 comprises an elongate housing whichclosely surrounds the glass barrel of the syringe. The annular flange 90at the rear of the syringe barrel rests on a barrel seat 91 at the rearof the syringe holder 9. The annular flange 90 at the rear of thesyringe barrel is often referred to as a “finger flange” because, duringa conventional (manual) injection using a syringe, the user's index andmiddle fingers rest naturally in front of the “finger flange” in orderto provide the necessary resistance to allow depression of the plungerby the thumb to deliver the medicament.

The barrel seat, for example in the form of an annular flange,preferably prevents forward axial movement of the syringe with respectto the syringe holder so that, in use, the syringe barrel and thesyringe holder move axially together as one unit.

In use, as described in WO 2005/070481, there are three stages ofdelivering an injection. Before delivering an injection (referring toFIG. 1 of the present application), the end cap 15 is pulled off,removing the needle cover 17 (if present) and rubber needle sheath 16with it from the needle. In the first stage of delivering an injection,as shown in FIG. 2 of the present application, the tags 7B at theforward end of the inner housing 7 are in contact with the syringebarrel 90, which is pushed axially forward (taking the syringe holder 9with it), so that the needle 10, which is fixed to the front end of thebarrel, moves in the direction indicated by the arrow so that eventuallyit protrudes beyond the nozzle 11 at the front of the device. Forwardtravel of the barrel and syringe holder is limited when a surface 9A ofthe syringe holder reaches an endstop 11A inside the nozzle or fronthousing 11.

Referring now to FIG. 3, the second stage of the injection is thedelivery of the medicament wherein the tags 7A at the rear of the innerhousing 7 depress the plunger 8 into the barrel of the syringe. Duringthis stage, the barrel of the syringe is held axially stationary, byabutment of the annular “finger” flange 90 against the barrel seat 91,which results in the barrel being placed in tension as the plungerpushes the non-compressible liquid medicament towards the forward end ofthe barrel. This tension is undesirable in a glass barrel, which maybecome damaged or broken, especially if the medicament comprises aparticularly viscous liquid which requires greater force to expel itfrom the syringe via the needle. Viscous medicaments are desirable incertain applications, where the use of a sustained-release viscousmedicament reduces the frequency that an injection is required.

It is desirable to minimise the diameter of the needle so far as ispossible, because the smaller the diameter of the needle, the lesspainful is the resulting injection. However, for a given length ofneedle, the smaller the needle diameter, the greater the force requiredto eject the medicament from the syringe.

It is also desirable to minimise the duration of the injection, i.e. tomaximise the speed at which the medicament is delivered from thesyringe. Particularly when the needle diameter is small, minimising theduration of the injection also means an increase in the force used toeject the medicament from the syringe.

An increase in the forces on the syringe consequently increases thelikelihood of the syringe breaking during the injection. The risk of thesyringe breaking during injection is significant, and is not onlyinconvenient and costly but is also potentially dangerous. If breakageoccurs, it is possible that glass fragments and/or the needle may becomedetached and exit the front of the device causing injury. Furthermore,there is the risk that the remaining medicament will leak or be ejectedfrom the device in an uncontrolled manner, potentially delivering thewrong dose into the patient, or causing injury e.g. if the medicamentcontacts the patient's skin or eyes. These problems are amplified whenthe medicament is viscous as a more powerful energy source is needed insuch applications so that the forces involved are greater. It is knownthat a typical breakage of the syringe during injection would occur atthe finger flange, whereby the finger flange 90 on the syringe barrelbreaks as a result of its abutment against the barrel seat 91. It istherefore highly desirable to minimise the likelihood of breakage of thesyringe.

In the third stage of the injection (not illustrated in the presentapplication but shown in WO 2005/070481), once the medicament has beendelivered and the inner housing 7 is no longer in contact with thebarrel or plunger of the syringe, the secondary spring 12 pushes thesyringe holder (and hence the syringe contained therein) axiallyrearwardly so as to retract the syringe back into the housing so thatthe used needle is concealed from view.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan autoinjector comprising a housing in which can be mounted a syringecomprising

a barrel for holding a volume of medicament,

a needle at one end of the barrel in fluid communication with themedicament,

a plunger axially-moveable in the barrel to a forwardmost position, theautoinjector further comprising

a needle sheath which seals the forwardmost end of the needle tomaintain sterility of the medicament within the barrel whereby, in use,the needle sheath must be removed from the needle immediately prior toactuating the autoinjector; and

a syringe support means for supporting the barrel at an axial locationat or forward of the forwardmost position of the plunger and having areaction surface for the syringe, whereby in use said reaction surfaceprovides an axial compressive force on said barrel when a forward axialforce is applied to the plunger.

Preferably, the autoinjector is a single-use autoinjector. The simpleconstruction of the autoinjector makes it very appropriate forapplications such as emergency use for injecting a large population tocontrol a pandemic, where a large number of cost-effective disposableautoinjectors are required. A single-use autoinjector also provides avery convenient means for patients to administer their own injections,even if lacking in dexterity and/or clinical experience. Delivery ofviscous drugs is particularly problematic for patients lacking dexteritybecause of the greater force needed to deliver such drugs—this problembeing alleviated by the present invention.

Typically, the autoinjector contains an energy source, for example acoiled spring, for moving said plunger axially in the barrel to deliveran injection in less than 30 seconds.

Preferably, the syringe is axially moveable in said housing and isbiased so that the needle is normally wholly inside said housing,wherein before injection the syringe is movable axially so as to move atleast a part of said needle out of the housing and wherein afterinjection, the syringe is able to retract in order to retract said partof said needle into the housing. The concealment of the needle bothbefore and after injection makes the autoinjector particularly suitablewhere the patient has any aversion to injection by needle. Retractionand retention of the needle after injection eliminates the risk ofneedle-stick injury.

According to a second aspect of the invention there is provided a methodof assembling an autoinjector comprising the steps of:

providing a first part-assembly comprising a front housing and a closelyfitting end cap;

providing a second part-assembly comprising a rear part of theautoinjector;

providing a syringe comprising a barrel for holding a volume ofmedicament, a needle at one end of the barrel and a plungeraxially-moveable in the barrel to a forwardmost position;

providing a syringe support means;

inserting the syringe axially into the rear end of the syringe supportmeans until said syringe support means supports the syringe;

inserting the front end of said syringe and syringe support means intosaid first part-assembly;

assembling said first part-assembly and second part-assembly together sothat said syringe support means supports the syringe at an axiallocation at or forward of the forwardmost position of the plunger,whereby in use said reaction surface provides an axial compressive forceon said barrel when a forward axial force is applied to the plunger.

According to a third aspect of the invention there is provided a methodof assembling an autoinjector comprising the steps of:

providing a first part-assembly comprising a syringe support means, afront housing and a closely fitting end cap;

providing a second part-assembly comprising a rear part of theautoinjector;

providing a syringe comprising a barrel for holding a volume ofmedicament, a needle at one end of the barrel and a plungeraxially-moveable in the barrel to a forwardmost position;

inserting the syringe axially into the rear end of the firstpart-assembly until said syringe support means supports the syringe;

assembling said first part-assembly and second part-assembly together sothat said syringe support means supports the syringe at an axiallocation at or forward of the forwardmost position of the plunger,whereby in use said reaction surface provides an axial compressive forceon said barrel when a forward axial force is applied to the plunger.

Further features of the invention are defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will now be moreparticularly described, by way of example only, with reference to theaccompanying drawings in which:

FIG. 1 (PRIOR ART) is a perspective view of a known injection device;

FIG. 2 (PRIOR ART) is a plan view, partly in section of the FIG. 1device, with the cap and needle cover removed, ready for actuation;

FIG. 3 (PRIOR ART) is a plan view, partly in section of the FIG. 1device, with the needle exposed, ready for the plunger to be depressedin order to deliver the medicament;

FIG. 4 is a perspective view of an injection device embodying one aspectof the present invention;

FIG. 5 is a plan view, partly in section of the FIG. 4 device, with thecap, needle cover and needle sheath removed, ready for actuation;

FIG. 6 is a plan view, partly in section of the FIG. 4 device, with theneedle exposed, ready for the plunger to be depressed in order todeliver the medicament;

FIG. 7 is a perspective view of the syringe holder;

FIG. 8 is a cross-sectional view of the syringe holder of FIG. 7;

FIG. 9 is a cross-section view of the syringe holder of FIG. 7, showinga syringe in place;

FIG. 10 is a cross-section view of the syringe holder of FIG. 7, showinga syringe, needle sheath and needle cover in place;

FIG. 11 shows detail, drawn to a larger scale, of the interface betweenthe front of the glass syringe barrel and the syringe holder illustratedin FIG. 10;

FIG. 12, drawn to a larger scale, is a cross-sectional view of themodified front housing;

FIG. 13, drawn to a larger scale, is a perspective cross-sectional viewof the front housing;

FIG. 14 is a cross-sectional view of the front housing, cap and syringeholder assembled together;

FIG. 15 is a perspective view of the front housing, cap and syringeholder assembled together;

FIG. 16 is a cross-sectional view of the front housing, cap, syringeholder and syringe assembled together;

FIG. 17 is a cross-sectional view of an alternative embodiment of thesyringe holder;

FIG. 18 is a part-assembly view showing the syringe holder of FIG. 17together with its spring retainer, a syringe therein and the end cap andfront housing;

FIG. 19 shows the part-assembly of FIG. 18 with the needle coverremoved;

FIG. 20 is a perspective view of the syringe holder of FIG. 17 togetherwith its spring retainer;

FIG. 21 is a perspective view of a syringe holder, end cap and fronthousing, showing an alternative means of retaining the gripping meansagainst the syringe barrel;

FIG. 22 is a perspective view of another embodiment of the syringeholder together with a needle cover.

DETAILED DESCRIPTION

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, means “including but not limited to”, andis not intended to (and does not) exclude other components, integers orsteps.

Throughout the description and claims of this specification, thesingular encompasses the plural unless the context otherwise requires.In particular, where the indefinite article is used, the specificationis to be understood as contemplating plurality as well as singularity,unless the context requires otherwise.

Throughout the following description, reference to a “forward” directionmeans the direction which is towards the patient when the injectiondevice is in use. The “forward” end of the injection device is the endnearest the patient's skin when the device is in use. Similarly,reference to a “rearward” direction means the direction which is awayfrom the patient and the “rearward” end of the device is the endfurthest from the patient's skin when the injection device is in use.

The “plunger” includes any elastomeric stopper or the like which sealsthe chamber containing liquid medicament. The plunger typically alsoincludes a plunger rod but this may be provided separately from theelastomeric stopper and need not be an essential part of the syringe.The “forwardmost position” of the plunger refers to the forwardmostposition of any part of the plunger (typically the forwardmost edge ofthe stopper).

Features, integers, characteristics or groups described in conjunctionwith a particular aspect, embodiment or example of the invention are tobe understood to be applicable to any other aspect, embodiment orexample described herein unless incompatible therewith.

As described above, a disadvantage of the known prior art is that thebarrel of the syringe is placed in tension as the plunger pushes thenon-compressible liquid medicament towards the forward end of the barrelfor delivery. This tension is undesirable in a glass barrel, which maybecome damaged or broken, especially if the medicament comprises aparticularly viscous liquid which requires greater force to expel itfrom the syringe. There is a possibility that the glass syringe mightbreak in the region of its finger flanges, as a result of the forces towhich it is subjected during delivery of an injection. One way tomitigate this problem is to reduce the effect of those forces in theregion of the finger flanges. For example, the syringe holder of WO2005/070481 can be modified by providing a helical slit at the rear endthereof which, in use, provides resilience to the region of the barrelseat on which is located the finger flange of the syringe (notillustrated). The resilient flexing absorbs shock and reduces the riskof breakage of the syringe in the region of the finger flanges.

Other means for reducing the effect of forces in the region of thefinger flanges can be envisaged, for example, providing a cushion in theform of an O-ring or moulding a relatively soft or elastomeric materialinto a harder substrate in the region of the barrel seat.

It is known that a typical breakage of the syringe during injectionwould occur at the finger flange, whereby the finger flange 90 on thesyringe barrel breaks as a result of its abutment against the barrelseat 91. However, the applicant has recognised that it is also possiblethat the syringe could break at points on the barrel forward of thefinger flange. This is potentially more serious as larger straight glassfragments may be ejected from the front of the device, as well as theunsecured needle, and any remaining medicament will leak out in anuncontrolled manner.

The risk of breakage or damage to the glass syringe may be reduced byensuring that the barrel is held in compression during delivery of themedicament (stage two of the injection process described in WO2005/070481), rather than being in tension. This can be achieved bysupporting the forward end of the barrel and having a reaction surfaceat which an axial compressive force can be applied to the barrel when aforward axial force is applied to the plunger during delivery of themedicament.

In the injection device of the present invention, the conventionalsyringe holder 9 is replaced with a more complex syringe holder which iscapable of supporting the syringe at the front end of its barrel insteadof at its rear flange 90 during delivery of the medicament. In theembodiment described below, the syringe holder supports the syringe atthe front shoulder of its barrel and provides a reaction surface therefor the front shoulder of the barrel. By “front shoulder” is meant theregion at which the largest diameter of the barrel reduces to a smallerdiameter at the nozzle. The front shoulder 92 is indicated in FIG. 9.Alternatively, the syringe could be supported and the reaction surfaceprovided at the front end of the syringe barrel, or at the narrowed“cone” where the needle is attached thereto and these embodiments aredescribed in more detail below. The syringe can, in fact, be supportedat any place on the barrel which, in use, is forward of the forwardmostposition of the fully-depressed syringe plunger and where a reactionsurface for the syringe can be provided (so that the barrel is held incompression throughout the delivery of the medicament).

However, the desired supporting or holding of the barrel by the syringeholder at its front end presents an assembly difficulty for a productwhere it is desired to keep manufacturing and assembly costs to aminimum. In the prior art device, the syringe can simply be dropped intothe rear end of the syringe holder until its flange 90 rests on thebarrel seat 91. This determines the axial position of the syringe withrespect to the syringe holder. In practice, the prior art syringe holderis supplied ready-assembled with the front part of the device, so thatthe pre-filled syringe can simply be dropped into the syringe holder andthen the front part of the device (including the syringe) can beattached to the ready-assembled rear part of the device in a simpletwo-stage assembly operation.

In the present invention, it is not possible to use the finger flange 90and barrel seat to determine the axial position of the syringe withrespect to the syringe holder. This is because the syringe holder needsto actively support the syringe at its front end (preferably at thefront shoulder 92 of the glass barrel). In the preferred embodimentthere are inwardly-directed gripping means to retain the front shoulderof the glass barrel at a specific axial location with respect to thesyringe holder. The standard syringe is usually supplied with a needlecover 17 which typically has a diameter almost the same as the largestdiameter of the glass barrel (see FIG. 10). The needle cover 17 may berigid, but is not necessarily so. Inside the needle cover 17, the needleis staked or spiked inside a needle sheath 16, which may be made fromrubber. If the syringe is inserted into the syringe holder needle-first(or rather needle-cover first), any inwardly-directed gripping meanswould foul on the needle cover (or needle sheath if no needle cover ispresent) as they attempt to pass. There is also the risk of the needlebeing damaged during assembly, for example if it is pushed into anyinwardly-directed gripping means. Such damage to the needle is highlyundesirable, as it could cause injury to the patient or could affect orimpede delivery of medicament, in particular because it often cannot bereadily detected if the needle is concealed within a needle cover and/ora rubber needle sheath. The damage to the needle may only becomeapparent during delivery of the medicament. The consequent effect of adamaged needle on delivery of medicament may not be apparent to thepatient at all.

This problem is solved by the use of a syringe holder 100 as illustratedin FIGS. 7 and 8. The syringe holder 100 comprises an elongate rearportion 102 in which there are viewing windows 103 so that themedicament chamber in the barrel of a syringe held therein would bevisible. There is a barrel seat 101 (equivalent to barrel seat 91 in theprior art device) at the rear end of the rear portion 102, but inpractice this is not intended to abut the flange 90 of the syringebarrel (unlike in the prior art device).

The syringe holder also has an intermediate portion 105 of comparablediameter to the rear portion, and a front portion 106 of narrowerdiameter. The intermediate portion 105 is provided with a discontinuousannular flange 104. Together, the intermediate and front portions 105,106 include radially-spaced slots 107 which define a plurality ofradially flexible fingers 108. In the illustrated embodiment, there arethree flexible fingers 108, but four or some other number of fingers maybe provided. FIG. 22 shows an embodiment in which four flexible fingers108 are provided on the syringe holder 100. The four fingers necessarilyeach are thinner than those in the three-finger embodiment. A typicalexample of a needle cover 17 is shown in FIG. 22 (illustrated withoutthe rest of the syringe for simplicity). The needle cover has a slot 17Atherein. If the syringe holder 100 is appropriately aligned with theneedle cover of a syringe held therein, there is a possibility that oneof the relatively thin flexible fingers 108 may undesirably snag or dropinto slot 17A, possibly causing damage to the underlying needle thatwould not become apparent until an injection is delivered. Thisdisadvantage can be overcome by ensuring that each of the flexiblefingers 108 is preferably wider than the needle cover slot 17A, asillustrated by the three-finger embodiment of FIG. 7.

As shown in FIG. 8, gripping means 109 preferably in the form of adiscontinuous annular inwardly-directed protrusion, are provided on theinterior of the flexible fingers 108 in the intermediate section 105.Referring to FIG. 9, when a syringe is located within the syringe holder100, the gripping means 109 abuts the front shoulder 92 of the barrel inorder to define the axial position of the barrel with respect to thesyringe holder.

The term “gripping means” is not limited to means which gripradially-inwardly onto the barrel, although in some embodiments they maydo so. More important is the fact that the gripping means 109 (orequivalent) supports the syringe in a desired axial location andprovides a reaction surface for the syringe so that the barrel will beheld in compression during delivery of the medicament.

As can be seen from FIGS. 10 and 11, the needle cover 17 has a greaterdiameter than the diameter normally available at the gripping means 109.In other words, the internal diameter between the gripping means 109 issmaller than the exterior diameter of the needle cover 17. However, aswill be explained in more detail below, when the syringe is insertedinto the syringe holder, as the needle cover 17 passes the grippingmeans 109, the flexible fingers 108 flex radially-outwardly to createsufficient diameter for the needle cover to pass the inwardly-protrudinggripping means, without exerting excessive force on the needle therein,thus minimising the risk of damage to the needle. Once the needle coverhas passed, the flexible fingers 108 spring back into their normalposition (having smaller internal diameter than the exterior diameter ofthe needle cover) and the gripping means 109 locate at the frontshoulder 92 of the barrel to provide the reaction surface against whichthe syringe will be held in compression during delivery of themedicament. In this position, the gripping means 109 are axially locatedbetween the needle cover and the front shoulder of the barrel.

The front portion 106 of the syringe support 100 is provided with aplurality of (preferably two) equispaced tags 110, whose purpose will bedescribed later below.

The most straightforward way to assemble the syringe and injectiondevice is in a three stage procedure, namely:

-   -   1. inserting the syringe into the syringe holder, until the        gripping means 109 locate at the front shoulder 92 of the        barrel;    -   2. inserting the syringe and syringe holder into the front part        of the injection device;    -   3. assembling the front part to the rear part of the injection        device.

Compared with the two-stage assembly procedure of the prior art device,the extra assembly stage is disadvantageous but initially seemsnecessary as it is not obvious how stages 1 and 2 could be readilycombined so that the syringe holder can be supplied ready-assembled withthe front part of the device. This is because, once assembled into thefront part of the device, the flexible fingers 108 would be preventedfrom flexing radially outwardly by their necessarily close abutment withthe front housing, thus preventing insertion of the syringe and needlecover.

Therefore, in a further embodiment of the invention, a modified fronthousing for the injection device is provided which enables a two-stageassembly procedure to be used.

The modified front housing 200 (analogous to nozzle 11 in the prior art)is illustrated in FIG. 12. The front housing 200 has a bore 201, ofsufficient diameter to allow passage therethrough of the needle 10,needle cover 17 and the front and intermediate portions 105, 106 of thesyringe holder (but not the flange 104).

The interior surface of the bore 201 is provided with two (or more)equispaced longitudinal slots 202, each having a rear section 203 with atapered surface providing a varying depth and a forward section 204 ofsubstantially constant depth. The boundary between the forward and rearsections of each slot 202 is defined by a step 205.

The slots 202 are positioned so that they can be aligned with the tags110 at the front portion of the syringe holder.

The slots 202 enable the syringe holder 100 to be assembled into thefront housing 200 at a specific axial position (relative to the fronthousing) so that the flexible fingers 108 stand clear of the fronthousing instead of being surrounded therein.

The slots 202 also provide radial location for the syringe holder 100 asit is inserted therein.

FIG. 14 shows a modified end cap 300 (analogous to end cap 15 in theprior art) designed for use with the modified front housing 200 and howthe syringe holder 100 is inserted into the front housing 200. The fronthousing 200 is inserted into the end cap 300 so that its leading surface206 abuts the interior of the end cap, so that no further forwardmovement of the front housing within the end cap is possible.

The close abutment of the end cap 300, front housing 200 and syringeholder 100 means that, if present, the needle cover 17 is retainedsecurely in position such that the risk of the needle cover accidentallybecoming loose or detached is minimised, thereby minimizing possibleloss of integrity of the seal between the rubber needle sheath and theneedle, which would otherwise compromise the sterility of the medicamentcontained within the syringe. The carefully engineered interactionbetween the components avoids the risk that during assembly, the syringeholder 100 might undesirably “snap” in between front end of the syringebarrel and the rear of the needle cover in such a way as to compromisethe seal between the end of the needle and the needle sheath in which itis staked.

The end cap has an upstanding annulus 301 which protrudes into and is aclose fit in the bore 201 of the front housing 200. The upstandingannulus 301 has two equispaced protrusions on the exterior surfacethereof which locate in longitudinal slots 202 when the end cap andfront housing are assembled together. Once assembled together, theupstanding annulus of the end cap and the step 205 together define aspace 302 into which tags 110 on the syringe holder 100 can locate.

In order to insert the syringe holder 100 into the front housing 200,the tags 110 are aligned with and pushed into the slots 202 until thetags 110 “click” over the step 205 and locate in the space 302. This isthe position illustrated in FIGS. 14 and 15. Now the syringe holder 100is suitably axially located such that the gripping means 109 andflexible fingers 108 are not constrained within the front housing 200and end cap 300.

The front housing, end cap and syringe holder are supplied in thisready-assembled condition, together with the ready-assembled rear partof the injection device, for final assembly with a pre-filled syringe.

It is therefore a straightforward two-stage procedure to finallyassemble the syringe into the device, namely:

-   -   1. inserting the syringe into the ready-assembled front housing,        end cap and syringe holder until the gripping means 109 locate        at the front shoulder 92 of the barrel (as shown in FIG. 16);    -   2. assembling the front part to the ready-assembled rear part of        the injection device (not illustrated).

FIGS. 4-6 show the fully assembled injection device including syringeholder 100. With reference to FIG. 5, it can be seen that (unlike in theprior art device) the flange 90 of the barrel does not contact thebarrel seat 101 of the syringe holder 100, there being a gap Gtherebetween. This is a result of the relative axial positions of thesyringe holder and syringe being determined at the front end, bygripping means 109 and front shoulder 92 and means that undesirabletension is not applied to the glass barrel during delivery of themedicament.

An alternative embodiment of the syringe holder is illustrated in FIGS.17-20. Where possible, the same reference numerals as were used inrelation to FIGS. 8-9 are used to identify like components of thealternative embodiment. Note that FIGS. 17-20 show the front end of thedevice at the left side of the Figures, whereas FIGS. 8-9 show the frontend of the device at the right side of the Figures.

In the FIG. 17 embodiment of the syringe holder 100′, theradially-flexible fingers 108′ have their free ends extending in theforward direction (compare with the radially-flexible fingers 108 inFIG. 8 which have their free ends extending in the rearward direction).The gripping means comprise inwardly-directed enlarged heads 109′ at theend of the flexible fingers 108. As is best seen in FIG. 19, theenlarged heads 109′ are capable of gripping the cone 93 at the front ofthe syringe barrel. The cone 93 is the region where the needle 10 isattached to the syringe barrel.

As shown in FIG. 18, when a syringe is assembled with the syringe holder100′, the needle cover 17 (which is of comparable diameter to thesyringe barrel) causes the flexible fingers 108′ to flexradially-outwardly so that the enlarged heads 109′ rest on the exteriorof the needle cover 17.

When the end cap 300 and needle cover 17 are removed axially in thedirection of the arrow in FIG. 18, the enlarged heads 109′ should moveradially-inwardly into contact with the cone 93 of the syringe so as togrip the front end of the barrel to provide the compressive force duringinjection. However, if the flexible fingers 108′ are made from plasticand if the device is stored in the FIG. 18 configuration for many monthsbefore use (both of which are likely), it is possible that the fingers108′ will no longer automatically flex properly inwardly upon removal ofthe needle cover 17.

Therefore, a spring retainer 111 is provided. The spring retainer 111 ismade from steel, other metal or other material which does notsignificantly lose its resilience over time. The spring retainer haselongate fingers which cooperate with the flexible fingers 108′ so as tourge them radially-inwardly. Once the needle cover 17 has been removed,the spring retainer 111 urges the enlarged heads 109′ into firm contactwith the cone 93 of the syringe, even if the flexible fingers 108′ areno longer capable of doing so. This position is illustrated in FIGS. 19and 20.

As illustrated in FIG. 21, the gripping means (109 or 109′) couldalternatively be provided in the form of a clip 112, inserted axiallyinto a slot 113 in the syringe holder so as to clip onto the front ofthe barrel.

Other means of providing a reaction surface for the front of the barrelso as to provide a compressive force during injection can be envisaged,for example a tapered elastomeric bush which could be snapped into placeonce the needle cover has passed during assembly. It may be possible togrip the frontmost part of the cone, where the needle enters the cone,rather than gripping the exterior thereof. Alternatively, other meansfor gripping the front shoulder of the barrel, or the exterior of thecone may be envisaged.

It is observed that the viewing windows 103, 103′ in the syringe holderare apertures which create space through which glass fragments couldmove in the event of a breakage. If a breakage occurs, it is highlydesirable to contain any glass fragments so as to minimise the risk ofinjury. Therefore, in an alternative embodiment (not illustrated), theapertures of the viewing windows are replaced by a solid but transparentor partially transparent material which still permits the user to viewthe interior of the syringe. Either the apertures 103, 103′ can be“filled” with a transparent material so as to form a window in the moreconventional sense of the word; alternatively, all of part of thesyringe holder may be manufactured from transparent or partiallytransparent material.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

All of the features disclosed in this specification (including anyaccompanying claims, abstract and drawings), and/or all of the steps ofany method or process so disclosed, may be combined in any combination,except combinations where at least some of such features and/or stepsare mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings), may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of any foregoingembodiments. The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

1. An autoinjector comprising a housing in which can be mounted asyringe comprising a barrel for holding a volume of medicament, a needleat one end of the barrel in fluid communication with the medicament, aplunger axially-moveable in the barrel to a forwardmost position, theautoinjector further comprising a needle sheath which seals theforwardmost end of the needle to maintain sterility of the medicamentwithin the barrel whereby, in use, the needle sheath must be removedfrom the needle immediately prior to actuating the autoinjector; and asyringe support means for supporting the barrel at an axial location ator forward of the forwardmost position of the plunger and having areaction surface for the syringe, whereby in use said reaction surfaceprovides an axial compressive force on said barrel when a forward axialforce is applied to the plunger.
 2. The autoinjector of claim 1 whereinsaid needle sheath substantially covers said needle to protect theneedle from mechanical damage.
 3. The autoinjector of claim 1 whereinsaid needle sheath entirely covers said needle and seals against thesyringe to maintain sterility of the external surface of the needle. 4.The autoinjector of claim 1 wherein said needle sheath comprises a solidelastomeric material into which the needle is spiked.
 5. Theautoinjector of claim 1 wherein said needle sheath is capable of beingremoved from the needle in an axially-forward direction immediatelyprior to actuating the autoinjector.
 6. The autoinjector of claim 1wherein said needle sheath is contained within a needle cover.
 7. Theautoinjector of claim 1 wherein said autoinjector is a single-useautoinjector.
 8. The autoinjector of claim 1 further comprising anenergy source for moving said plunger axially in the barrel to deliveran injection in less than 30 seconds.
 9. The autoinjector of claim 1wherein the syringe is axially moveable in said housing and is biased sothat the needle is normally wholly inside said housing, wherein beforeinjection the syringe is movable axially so as to move at least a partof said needle out of the housing and wherein after injection, thesyringe is able to retract in order to retract said part of said needleinto the housing.
 10. The autoinjector of claim 1 wherein, in use, saidreaction surface provides an axial compressive force to a front shoulderof the syringe barrel.
 11. The autoinjector of claim 1 wherein, in use,said reaction surface provides an axial compressive force to a frontcone of the syringe barrel.
 12. The autoinjector of claim 1 wherein saidsyringe support means includes one or more inwardly-directed protrusionsforming said reaction surface.
 13. The autoinjector of claim 12 whereinsaid inwardly-directed protrusions are on the end of one or moreradially-flexible fingers.
 14. The autoinjector of claim 13 wherein saidinwardly-directed protrusions comprise an inwardly-directed enlargedhead on each radially-flexible finger.
 15. The autoinjector of claim 13further comprising a spring retainer, preferably made from steel, forurging each radially-flexible finger inwardly.
 16. The autoinjector ofclaim 12 wherein the internal diameter between said inwardly-directedprotrusions is smaller than the exterior diameter of the syringe barrel.17. The autoinjector of claim 16 wherein, when the autoinjector is fullyassembled ready for use, said inwardly-directed protrusions are axiallylocated between a needle cover and the front shoulder of the syringebarrel.
 18. The autoinjector of claim 1 wherein said syringe supportmeans is generally cylindrical and of a diameter less than a diameter ofa finger flange of the syringe barrel so that the syringe support meansis suitably sized to closely surround the barrel of the syringe, in use.19. The autoinjector of claim 1 wherein said syringe support means iscapable of supporting said syringe barrel at a specific axial locationwith respect thereto.
 20. The autoinjector of claim 1 wherein saidsyringe support means includes one or more viewing windows, to permit auser to view the barrel of a syringe supported therein.
 21. Theautoinjector of claim 20 wherein said one or more viewing windowscomprise one or more apertures in the syringe support means.
 22. Theautoinjector of claim 20 wherein said one or more viewing windowscomprise a transparent or partially transparent part of the syringesupport means.
 23. The autoinjector of claim 1 wherein said syringesupport means further comprises one or more alignment tags at the frontend thereof.
 24. The autoinjector of claim 23 further comprising a fronthousing having a bore therethrough, the interior surface of the borebeing provided with one or more longitudinal slots, positioned so thatsaid alignment tags can locate therein, when said front housing andsyringe support means are assembled together.
 25. The autoinjector ofclaim 24 wherein each longitudinal slot comprises a rear section havinga forwardly-increasing depth and a forward section having substantiallyconstant depth.
 26. The autoinjector of claim 25 wherein a boundarybetween the rear and forward sections is defined by a step.
 27. Theautoinjector of claim 26 further comprising an end cap having internalprotrusions therein which protrude into the longitudinal slots in thebore of the front housing, when said end cap and said front housing areassembled together, so that a space is defined between said internalprotrusions in the end cap and said step in the front housing.
 28. Theautoinjector of claim 27 wherein the alignment tags of the syringesupport means locate into said defined space to determine an axiallocation of the syringe support means with respect to said fronthousing.
 29. The autoinjector of claim 24 wherein said syringe supportmeans includes a radially-extending flange, of greater diameter than aninterior diameter of said front housing.
 30. The autoinjector of claim27 wherein, when assembled together, said end cap, front housing andsyringe support substantially prevent damage to or movement of a needlecover and/or said needle sheath on the needle of a syringe mounted inthe device.
 31. The autoinjector of claim 18 wherein the finger flangeof the syringe barrel does not contact the syringe support means duringdelivery of the medicament.
 32. The autoinjector of claim 13, whereinsaid radially-flexible fingers can flex sufficiently outwardly to allowa needle cover, said needle sheath or the like of larger diameter thanthe internal diameter between said radially-flexible fingers to passthereby during assembly of a syringe into said autoinjector.
 33. Theautoinjector of claim 28 wherein said radially-flexible fingers can flexsufficiently outwardly to allow a needle cover, said needle sheath orthe like of larger diameter than the internal diameter between saidradially-flexible fingers to pass thereby during assembly of a syringeinto said autoinjector, and wherein said axial location of the syringesupport means with respect to the front housing is such that saidradially-flexible fingers are not confined within said front housing andare free to flex radially, when the front housing and syringe supportmeans are assembled together and before assembly of a rear part-assemblyof the autoinjector thereto.
 34. The autoinjector of claim 32 wherein,when the device is fully assembled ready for use, said inwardly-directedprotrusions closely abut the needle cover and/or said needle sheath toreduce the risk of said needle sheath becoming loose or detached fromthe needle, potentially compromising the sterility of the needle. 35.The autoinjector of claim 1 wherein the housing is an outer housing andat least part of the needle is axially moveable in and out of said outerhousing but is biased to be normally wholly inside said housing, theautoinjector further comprising: an inner housing intermediate the outerhousing and the barrel and plunger; and an energy source incommunication with said inner housing, wherein the inner housing ismoveable by the energy source between three positions, namely a firstposition in which the inner housing is in communication with the barrelsuch that, in use, the plunger and barrel are movable axially so as tomove at least part of said needle out of the outer housing; a secondposition in which the inner housing is in communication with the plungerbut not the barrel such that, in use, said plunger is movable axiallyinto said barrel so as to expel medicament through the needle; and athird position in which the inner housing is in communication withneither the plunger nor the barrel such that, in use, the plunger andbarrel are able to retract in order to retract the needle into the outerhousing.
 36. The autoinjector of claim 35 wherein said inner housingincludes one or more flexible tags, biased radially inwardly bycommunication with said outer housing.
 37. The autoinjector of claim 36wherein one or more of said tags are situated at a rear end of the innerhousing and are biased radially inwardly into communication with theplunger.
 38. The autoinjector of claim 37 wherein each rear tag ismoveable out of communication with the plunger when aligned with acorresponding recess in the outer housing.
 39. The autoinjector of claim36 wherein one or more of said tags are situated at a forward end of theinner housing and are biased radially inwardly into communication withthe barrel.
 40. The autoinjector of claim 39 wherein each forward tag ismoveable out of communication with the barrel when aligned with acorresponding recess in the outer housing.
 41. The autoinjector of claim1, in which is mounted a syringe comprising a barrel for holding avolume of medicament, a needle at one end of the barrel in fluidcommunication with said medicament and a plunger axially-moveable in thebarrel to a forwardmost position.
 42. (canceled)
 43. A method ofassembling an autoinjector comprising the steps of: providing a firstpart-assembly comprising a front housing and a closely fitting end cap;providing a second part-assembly comprising a rear part of theautoinjector; providing a syringe comprising a barrel for holding avolume of medicament, a needle at one end of the barrel and a plungeraxially-moveable in the barrel to a forwardmost position; providing asyringe support means having a reaction surface for the syringe;inserting the syringe axially into the rear end of the syringe supportmeans until said syringe support means supports the syringe; insertingthe front end of said syringe and syringe support means into said firstpart-assembly; assembling said first part-assembly and secondpart-assembly together so that said syringe support means supports thesyringe at an axial location at or forward of the forwardmost positionof the plunger, whereby in use said reaction surface provides an axialcompressive force on said barrel when a forward axial force is appliedto the plunger.
 44. A method of assembling an autoinjector comprisingthe steps of: providing a first part-assembly comprising a syringesupport means, a front housing and a closely fitting end cap; providinga second part-assembly comprising a rear part of the autoinjector;providing a syringe comprising a barrel for holding a volume ofmedicament, a needle at one end of the barrel and a plungeraxially-moveable in the barrel to a forwardmost position; inserting thesyringe axially into the rear end of the first part-assembly until saidsyringe support means supports the syringe; assembling said firstpart-assembly and second part-assembly together so that said syringesupport means supports the syringe at an axial location at or forward ofthe forwardmost position of the plunger, whereby in use said reactionsurface provides an axial compressive force on said barrel when aforward axial force is applied to the plunger.
 45. (canceled)